Abstract: A total of 33 layers of T2 copper and 65Mn steel multilayer composite specimens with thickness of 15 mm were successfully fabricated using vacuum diffusion welding. The microstructure of composite interface and element diffusion behavior of the specimens were observed and analyzed by metallography microscope and electron microscope. The mechanical properties were studied by tensile, bending and impact tests. The results show that the composite interface is straight and the combination effect is great with the meshing characteristic between layers. Cu and Fe elements are diffused near the interface, and the diffusion layer thickness is about 2.7 μm. The heterogeneous interface results in the passivation, deflection and bifurcation of cracks, which improves the crack propagation resistance of multilayer composites. And the tensile strength, yield strength and elongation are 463.3 MPa, 296.4 MPa and 14.8%, respectively. The bending strength is 942.3 MPa. The impact energy shows anisotropy, holding 94.5 J in arrester direction and 28.2 J in divider direction. Due to the large difference in component properties, the multilayer composites show different fracture forms, including cleavage fracture in copper layer and ductile fracture in steel layer.